Question

The average monthly salary of 500 teachers of Candelaria East district is

P26,500. If the monthly salaries of the teachers are normally distributed with

standard deviation of P2,500, approximately how many teachers in the district

are earning more than P30,000 monthly?

Answer 1

z=$\frac{x-sample\space mean }{s/\sqrt n}$

n=500

sample mean =26500

standard deviation =2500

x=30000

P(more than 30000)=?

P(x>30000)=1-P(x$\le$ 30000)

z=$\frac{30000-26500}{2500/\sqrt{500}}$

z=31.30

p(z$\le$31.30)=1

P(x>30000)=0

Thus none of the teachers earn more than P 30000 monthly